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UNLV Retrospective Theses & Dissertations
1-1-2004
Elevated temperature mechanical properties and corrosion Elevated temperature mechanical properties and corrosion
characteristics evaluation of alloy Ht-9 characteristics evaluation of alloy Ht-9
Bhagath Yarlagadda University of Nevada, Las Vegas
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Repository Citation Repository Citation Yarlagadda, Bhagath, "Elevated temperature mechanical properties and corrosion characteristics evaluation of alloy Ht-9" (2004). UNLV Retrospective Theses & Dissertations. 1707. http://dx.doi.org/10.25669/doqp-evj5
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ELEVATED TEMPERATURE MECHANICAL PROPERTIES AND CORROSION
CHARACTERISTICS EVALUATION OF ALLOY HT-9
by
Bhagath Yarlagadda
Bachelor of Technology in Mechanical (Manufacturing) Engineering J.N.T.U. College of Engineering, Hyderabad, India
June 2002
A thesis submitted in partial fulfillment of the requirements for the
Master of Science Degree in Mechanical Engineering Department of Mechanical Engineering
Howard R Hughes College of Engineering
Graduate College University of Nevada, Las Vegas
August 2004
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UMI Number: 1422890
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ITNTV Thesis ApprovalThe Graduate College University of Nevada, Las Vegas
July 15 20 04
The Thesis prepared by
B hagath Y arlagad d a
Entitled
Elevated Temperature Mechanical Properties and CorroRion
C h a r a c t e r i s t i c s E v a liia t to n o f A l l o y HT-Q.
is approved in partial fulfillment of the requirements for the degree of
M aster o f S c ie n c e in M e ch a n ica l E n g in e e r in g .______
Examination Committee M em ber
£Examination Committee M em ber
Graauate C rllege Faculty Representative
Examination Committee Chair
Dean of the Graduate College
11
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ABSTRACT
Elevated Temperature Mechanical Properties and Corrosion CharacteristicsEvaluation Alloy HT-9
by
Bhagath Yarlagadda
Dr. Ajit K.Roy, Examination Committee Chair Associate Professor of Mechanical Engineering
University of Nevada, Las Vegas
This thesis presents the results of tensile testing, stress corrosion cracking (SCC) and
localized corrosion studies of Alloy HT-9, which is currently being considered as a target
structural material for transmutation applications. The results of tensile testing indicate
that the yield strength and the ultimate tensile strength were gradually reduced with
increasing temperature, but the ductility parameters were enhanced due to increased
plastic deformation, irrespective of the tempering time. The results of SCC testing in the
90°C acidic solution, performed by the slow-strain-rate (SSR) technique, revealed higher
failure stress (of) at longer tempering time. Localized corrosion studies conducted by
polarization technique showed pitting and crevice corrosion in specimens exposed to both
neutral and acidic environments. The fractographic evaluations of the primary fracture
face of the broken tensile specimen by scanning electron microscopy revealed dimpled
microstructure indicating ductile failure. Branched secondary cracks were observed along
the gage length of the SCC test specimens, evaluated by optical microscopy.
Ill
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TABLE OF CONTENTS
ABSTRACT.............................................................................................................................iii
LIST OF TABLES..................................................................................................................vi
LIST OF FIGURES................................................................................................................vii
ACKNOWLEDGEMENTS................................................................................................... ix
CHAPTER I INTRODUCTION..............................................................................................1
CHAPTER 2 MATERIALS AND ENVIRONMENTS..................................................... 72.1 Test Materials........................................................................................................... 72.2 Test Specimens........................................................................................................102.3 Test Environments.................................................................................................. 12
CHAPTER 3 EXPERIMENTAL PROCEDURES..............................................................133.1. Tensile Testing....................................................................................................... 133.2. Slow-Strain-Rate Testing....................................................................................... 173.3. Cyclic Potentiodynamic Polarization Testing...................................................... 213.4. Optical Microscopy.................................................................................................243.5. Scanning electron microscopy...............................................................................24
CHAPTER 4 RESULTS........................................................................................................264.1 Hardness vs. Tempering Time................................................................................264.2 Ambient-Temperatnre Mechanical Properties...................................................... 264.3 Elevated Temperature Tensile Testing..................................................................274.4 Fractographic Evaluations......................................................................................344.5 Slow Strain Rate (SSR) Testing............................................................................. 364.6 Localized Corrosion Study.....................................................................................394.7 Metallographic Evaluations....................................................................................43
CHAPTER 5 DISCUSSIONS..............................................................................................465.1 Effect of Thermal-Treatment................................................................................. 465.2 Effect of Temperature on Tensile Properties........................................................ 475.3 Slow Strain Rate Testing........................................................................................48
CHAPTER 6 SUMMARY AND CONCLUSIONS...........................................................50
CHAPTER 7 FUTURE W ORK.......................................................................................... 52
IV
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APPENDIX A: TENSILE DATA USING SPECIMENS TEMPERED FOR1.25 HOURS............................................................................................... 53
APPENDIX B: TENSILE DATA USING SPECIMENS TEMPERED FOR1.75 HOURS............................................................................................... 58
APPENDIX C: TENSILE DATA USING SPECIMENS TEMPERED FOR2.25 HOURS............................................................................................... 63
APPENDIX D: SEM MICROGAPHS FOR SPECIMENS TEMPERED FOR1.25 HOURS............................................................................................... 68
APPENDIX E: SEM MICROGAPHS FOR SPECIMENS TEMPERED FOR1.75 HOURS............................................................................................... 69
APPENDIX F: SEM MICROGAPHS FOR SPECIMENS TEMPERED FOR2.25 HOURS............................................................................................... 70
BIBLIOGRAPHY................................................................................................................... 71
V ITA........................................................................................................................................73
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LIST OF TABLES
Table 2.1 Physical and Thermal Properties of Alloy HT-9................................................... 9
Table 2.2 Chemical Composition (%wt) of Alloy HT-9......................................................10
Table 2.3 Chemical Composition of Test Environments (gram/liter).................................12
Table 3.1 Minimum Times Needed to Reach the Desired Temperature............................ 16
Table 4.1 Hardness Due to Thermal Treatments..................................................................26
Table 4.2 Ambient Temperature Tensile Properties of Alloy HT-9................................... 27
Table 4.3 UTS and YS of Alloy HT-9 at Different Temperatures..................................... 30
Table 4.4 %E1 and %RA of Alloy HT-9 at Different Temperatures.................................. 30
Table 4.5 YS vs. Uniform Strain at Different Temperatures............................................... 31
Table 4.6 Results of SSR Testing.......................................................................................... 37
Table 4.7 CPP Test Results.................................................................................................... 43
VI
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LIST OF FIGURES
Figure 1.1 Approach to Spent Fuel Management..............................................................2
Figure 1.2 Different Components of Idealized Transmutation System........................... 3
Figure 1.3 Separation of Fission Products and Actinides................................................. 4
Figure 2.1 Schematic View of Smooth Cylindrical Tensile Specimen..........................11
Figure 2.2 Polarization Specimen..................................................................................... 11
Figure 3.1 Material Testing System (MTS)......................................................................15
Figure 3.2 CERT Machine for SSR Testing.....................................................................18
Figure 3.3 SSR Test Setup Showing Different Components...........................................18
Figure 3.4 Load Frame Compliance Test Data.................................................................19
Figure 4.1 Comparison of Stress-Strain Diagrams for at Different Temperatures 28
Figure 4.2 Comparison of Stress-Strain Diagrams at Different temperatures...............28
Figure 4.3 Comparison of Stress-Strain Diagrams at Different Temperatures..............29
Figure 4.4 UTS vs. Temperature........................................................................................31
Figure 4.5 YS vs. Temperature..........................................................................................32
Figure 4.6 %E1 vs. Temperature........................................................................................32
Figure 4.7 %RA vs. Temperature......................................................................................33
Figure 4.8 Uniform Strain vs. Temperature......................................................................33
Figure 4.9 SEM Micrograph of Alloy HT-9 at Room Temperature for SpecimenTempered for 1.25 hrs (35X)........................................................................ 34
Figure 4.10 SEM Micrograph of Alloy HT-9 at 600°C for Specimen Temperedfor 1.25 hrs (35X).......................................................................................... 34
Vll
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Figure 4.11 SEM Micrograph of Alloy HT-9 at Room Temperature for SpecimenTempered for 1.75 hrs (35X)........................................................................ 35
Figure 4.12 SEM Micrograph of Alloy HT-9 at 600°C for Specimen Temperedfor 1.25 hrs (35X)..........................................................................................35
Figure 4.13 SEM Micrograph of Alloy HT-9 at Room Temperature for SpecimenTempered for 2.25 hrs (35X)........................................................................ 35
Figure 4.14 SEM Micrograph of Alloy HT-9 at 600°C for Specimen Temperedfor 2.25 hrs (35X).......................................................................................... 35
Figure 4.16 Failure Stress vs. Tempering Time................................................................. 37
Figure 4.17 Time to Failure vs. Tempering Time..............................................................38
Figure 4.18 %E1 vs. Tempering Time.................................................................................38
Figure 4.19 %RA vs. Tempering Time...............................................................................39
Figure 4.20 Calibration Curve using GAMRY Potentiostat............................................. 40
Figure 4.21 CPP Diagram in 30°C Neutral Solution........................................................41
Figure 4.22 CPP Diagram in 90°C Neutral Solution........................................................41
Figure 4.23 CPP Diagram in 30°C Acidic Solution.......................................................... 42
Figure 4.24 CPP Diagram in 90°C Acidic Solution.......................................................... 42
Figure 4.25 Epit vs. Temperature........................................................................................43
Figure 4.26 Optical Micrographs of Alloy HT-9 under Different Heat-Treat Conditions
................................................................................................................... 44
Figure 4.27 Optical Micrographs of Tensile Specimens Tempered for 1.25 hours.........45
Figure 4.28 Optical Micrographs of SSR Test specimens in 90°C Acidic Solution........45
vm
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ACKNOWLEDGEMENTS
First and foremost, I wish to thank Dr. Ajit K.Roy, my research advisor, for his
valuable guidance, and for having been a constant source of inspiration for this work. I
really admire Professor Dr. Ajit K.Roy’s dedication to his research; I have learned a lot
from his approach of conducting research.
I also thank Dr. Anthony Hechanova, Director of Transmutation Research Program
(TRP), Dr. Brendan J.O’toole, Department of Mechanical Engineering and Dr.
Venkatesan Muthukumar, Department of Electrical & Computer Engineering, UNLV, for
their direct and indirect contributions for the research and serving on my thesis
committee. I would also like to thank Dr. Mohamed B.Trabia, chairman of department of
mechanical engineering,.
Acknowledgement is made to the support of the United States Department of Energy
(USDOE) under contract no: DEFG042001AL67358.
I would like to thank my parents, Mr. Subba Rao and Mrs. Chandra Sahaja for all
their support and belief in me, and my brother Pramod for supporting me during rough
times.
I would like to acknowledge the support and help of my friends, Srinivasa Rao
Kukatla, Venkata Nagarjuna Potluri, Satish Babu Dronavalli, Narendra Kothapalli,
Suresh Babu Sadineni, Sudheer Sama and many colleagues throughout this research.
IX
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CHAPTER 1
INTRODUCTION
Over the past two decades, extensive efforts have been focused to determine the
suitability of the Yucca Mountain site, near Las Vegas, Nevada to contain highly
radioactive nuclear waste inside a geologic repository. The purpose of this repository is to
safely dispose highly radioactive nuclear waste such as spent nuclear fuel (SNF) and
defense high-level-radioactive waste (HLW) for at least 10,000 years. The primary goal
to build this repository is to isolate the SNF/HLW from the near-field environment.^’
Nuclear waste is comprised of used fuel discharged from operating nuclear reactors.
Currently, nearly 20% of the nation’s electricity is being produced from nuclear power
using the existing operating plants. Over 87,000 metric tons of SNF are expected to be
produced from approximately 100 operating nuclear power plants over their lifetimes in
the proposed Yucca Mountain repository. Approximately 70,000 tons of SNF and HLW
are designed to be disposed of in Yucca Mountain. This amount represents nuclear waste
produced by the past and present day reactors. However, by the year 2050, almost 1
million tons of nuclear waste may require disposal worldwide. Such projection would
indicate the need to build and commission a repository of the scale of the Yucca
Mountain somewhere in the world roughly every three to four years.
Actually, in the SNF, only about 1% of its content is harmful. Therefore, this 1%
poses a severe risk to the future generations, requiring long-term disposal of these
1
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hazardous materials. This 1% of SNF is primarily made up of americium (Am),
plutonium (Pu), neptunium (Np) and curium (Cm), and also long-lived isotopes of iodium
(I) and technetium (Tc) created as by-products resulting from the fission process inside
the nuclear reactors. Am, Pu, Np and Cu are called as trasuranic elements. The long term
toxicity of the nuclear waste depends on these transuranic elements. The toxic nature of
SNF can be reduced below that of uranium ore within a period of several hundred of
years by removing these transuranic elements from SNF/HLW. Different approaches
proposed for spent fuel management are shown in Figure 1.1.
Spent Fuel Fmrn OommerdalPlmib r
OkeotDisposa
Spentfuel
Recytie
PU
Tam, «vaneat,
Residing
--- -- - ► OUREX ----- * SiparMlcnsP i\/u ra n lu m P u A / u r a i u m
W M deYRecyrle ^
(Existing Fleet)
Long Tam
m yssPu AcUmües
PmductsmepD$#y
J Transuîiter , (laênlVFaAReaiA:/I ÂtceteratorDiwenSysieiw)
t Tmoe PuL TmceAdlnldes
FisekmPittWt %@Wtov
Figure 1.1 Approach to Spent Fuel Management
Removal of Pu and other transuranic elements from SNF can minimize the long-term
heat management issues within the geologic repository. The possibility of penetration of
radioactive materials into the biosphere in future can be reduced or eliminated by
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removal of Np, Tc and I. Further, the removal of Pu from the SNF could enable the
recovery of Pu for nuclear proliferation. In essence, the development of a large nuclear
waste repository is driven by the presence of this small amount of long-lived highly toxic
materials contained in SNF. Thus, in order to store the SNF for a much shorter duration
in the potential repository, and to avoid construction of additional geologic repository in
future, these long-lived isotopes and fission products must be minimized or eliminated.
This goal can be accomplished through a process known as transmutation. Different
stages involved in the transmutation process are shown in Figure
s p a t t i
JL.
rqpm«c«M
■pu, MkmcAc-tinittes
fud ?
t r a n s m w l a l i o n r e a K t e r
Eadwmjclidt» Impsacliœa! to Tt:aasmute
s h f i r t a m S m c d i u m - l i v e i t - » S s s i o a p r o j e t s
noit ttanwritMatlK» wiâ
W a s t e M a i H f a n a A
storage for centtirks Of repositoty
t o w 4 s » t e l w a s t e c sposal
{ioteimctWetevd w a s t e d i s p o s a l
Figure 1.2 Different Components of Idealized Transmutation System
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Transmutation occurs when the nucleus of an atom changes because of natural
radioactive decay, nuclear fission, nuclear fusion, neutron capture, or numerous other
processes. The United States transmutation program objective is to transform the long-
lived actinides and fission products into stable or significantly shorter-lived nuclides. The
goal is to have wastes, which may become radiologically innocuous in only a few
hundred years. Elimination or minimization of long-lived actinides and fission products
irom SNF is accomplished by impingement of neutron flux onto it, thus inducing
transmutation. Most transmutation processes involve the use of nuclear reactors or
particle accelerators. Some radiotoxic nuclides, such as Pu-239 and the long-lived fission
products Tc-99 and 1-129, can be transmuted (fissioned, in the case of Pu-239) with
thermal (slow) neutrons. The process of separation of fission products (FP) and minor
actinides (MA) are shown in Figure 1.3.
Initial Materials: UraniumCladding & Structures
fp
/ I I
n
f i
fp
uPu or MA
e è fp
Resulting Materials:UraniumPlutonium & Minor Actinides (MA)Fission ProductsActivated Cladding & Structures
X \ •Pu or \ U
• i'-èPu or • w MA \ U
Figure 1.3 Separation of Fission Products and Actinides
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The minor actinides including Np, Am and Cm, and the higher isotopes of Pu, which
are all highly radiotoxic, can be more readily destroyed by fissioning with a fast-neutron
energy spectrum, where they can also contribute to the generation of power
With repeated recycling in a transmutation system, the radiotoxicity of SNF can be
reduced to a point that, after a decay period of less than 1000 years, it is less toxic than
the uranium ore originally used to produce the fuel. The need for a waste repository is
certainly not eliminated, but the hazard posed by the disposed waste materials is greatly
reduced, thus, requiring shorter disposal period.
Transmutation involves bombarding a target material such as molten lead-bismuth-
eutectic (LBE) by protons generated by an accelerator, thereby producing neutrons or in a
nuclear reactor. These neutrons are then impinged upon HLW and SNF at a very high
speed, thus minimizing or isolating highly radioactive isotopes and fission products. This
enables the storage of SNF/HLW for much shorter durations in the repository due to their
reduced half-lives. The advantages associated with the use of a transmutation process are
the reduction of the volume, toxicity and fissile content of the waste requiring disposal,
minimization of materials that may create proliferation and environmental risks, and
development of a simple repository. During transmutation, significant amounts of heat
can be generated in the target material (molten LBE). However, the molten LBE will be
contained in a sub-system structural container made of a martensitic stainless steel, such
as Alloy HT-9. Since the molten LBE will be subjected to stresses during neutron
generation at elevated temperatures ranging between 400 and 600°C, the target structural
material (Alloy HT-9) may also undergo plastic deformation in this temperature regime.
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Thus, this investigation is focused on the evaluation of the tensile properties of
martensitic Alloy HT-9 at elevated temperatures. Mechanical properties of Alloy HT-9
have been evaluated using a mechanical testing system (MTS) in the presence of nitrogen
at temperatures ranging from ambient to 600°C as a function of different tempering times.
Corrosion studies have also been performed to evaluate the stress corrosion cracking
(SCC) and localized corrosion (pitting and crevice) behavior of this alloy. Metallurgical
microstructures, and the extent and morphology of failures at different testing
temperatures were analyzed by optical microscopy and scanning electron microscopy
(SEM), respectively.
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CHAPTER 2
MATERIALS AND ENVIRONMENTS
2.1 Test Materials
The material tested in this study is Alloy HT-9 which is a martensitic stainless steel.
Alloy HT-9 is also called a 12Cr-lMoVW steel. It has a high chromium (Cr) content of
about 12%. Hence Alloy HT-9 is also called a high-chromium martensitic stainless steel.
Presence of increased Cr content in this steel provides excellent resistance to atmospheric
corrosion and resistance to degradation in many organic media. The presence of
molybdenum (Mo) enhances the localized corrosion resistance in environments
containing deleterious species by preventing the breakdown of protective oxide films.
Alloy HT-9 has a body-centered-cubic (BCC) structure. Physical and thermal properties
of this alloy are given in the Table 2.1.
Martensitic stainless steels are considered to be potential candidates for the blanket
and first wall structures of a fusion reactor. "* Several factors need to be considered in
selecting the structural material for transmutation applications. These factors include
mechanical, thermal, physical and chemical properties, cost, availability, capability of
withstanding radiation damage and some neutronic factors. Alloy HT-9 can be used up to
a temperature of 500°C in Pb-Li coolant.^^^
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Martensitic alloys are also finding increased application in the fast breeder reactor
systems. Alloy HT-9 possesses better corrosion and swelling resistance and provides
excellent resistance to irradiation embrittlement at 60°C. A major concern on the effect of
extremely high electromagnetic fields on a ferromagnetic structure was alleviated when it
was realized that a ferromagnetic material would behave paramagnetically in an
extremely strong magnetic field.
Martensitic stainless steels have been developed for both in-core applications in
advanced liquid metal fast breeder reactors (LMFBR) and for first wall and structural
materials applications for commercial fusion reactors. Alloy HT-9 has been extensively
tested for LMFBR applications and has shown to resist radiation damage, providing a
creep and swelling resistant alternative to austenitic stainless steels. Degradation in
fi-acture toughness and charpy impact properties have been observed with this alloy, but
these properties are sufficient to provide reliable service performance. Tungsten-
stabilized martensitic stainless steels have appropriate properties for fusion applications.
Radioactivity levels become benign after less than 500 years of service, giving excellent
radiation damage resistance. Moderate strength, ample corrosion resistance, and excellent
resistance to swelling in the fast neutron environment has made Alloy HT-9 a primary
candidate material for use as cladding in the current U.S. fast reactor designs.^^^
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Table 2.1 Physical and Thermal Properties of Alloy HT-9
Property Value
Thermal Conductivity, W/m*K 28
Modulus of Elasticity, Gpa (10^ psi) 160
Poisson’s Ratio 0.33
Coefficient of Thermal Expansion per °C (°F) * 10 ^ 12.5
Experimental heats of Alloy HT-9, tested in this investigation, were melted by a
vacuum-induction-melting practice at the Timken Research Laboratory, Canton, OH,
followed by different fabricating processes that included forging, hot rolling and cold
rolling. Since significant amount of residual or internal stresses were generated during
these manufacturing processes, the test materials were subsequently thermally-treated to
relieve these internal stresses and achieve the desired metallurgical microstructures.
These thermal treatments included austenitizing at 1850°F, followed by an oil-quench
(OQ). Subsequently, they were tempered at 1150°F, followed by air-cooling (AC). These
types of thermal-treatments resulted in a fully-tempered fine-grained microstructure
characteristics of a martensitic stainless steel without the formation of any retained
austenite. The chemical compositions of two experimental heats of Alloy HT-9 are
shown in Table 2.2.
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Table 2.2 Chemical Composition (%wt) of Alloy HT-9
Material / Heat No.
C Mn P S Si Cr Ni Mo Cu V W
HT-92048
0.18 0.40 .012 0.004 0.20 12.6 0.49 1.00 0.01 0.30 0.46
HT-92049
0.19 0.41 0.012 0.004 0.20 12.31 0.50 1.00 0.01 0.30 0.47
2.2 Test Specimens
The heat-treated materials, in the form of round bars, were subsequently machined to
fabricate smooth cylindrical specimens having 4-inch overall length, 1-inch gage length
and 0.25-inch gage diameter, as illustrated in Figure 2.1. These specimens were machined
in such a way that the gage section was parallel to the longitudinal rolling direction. The
gage length to the diameter (1/d) ratio of these specimens was maintained at 4 according
to the ASTM Designation E 8 .^ The tensile properties were determined by using these
specimens in an MTS machine (Model 319.25). Specimens for localized corrosion
studies were also manufactured from these materials according to the ASTM designation
G 5. * Since the corrosion properties of engineering materials depend on the surface
finish of the test specimens, the polarization specimens were properly polished prior to
their testing. The schematic view of the polarization specimen is shown in Figure 2.2.
10
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7 /1 6 - 2 0 UNF-2AIZ^ôîTbI# 3 CENTER DRILL
BOTH ENDS (OPTIONAL)
R ~ 0 .Q 01[^
L a b e l to o th e n d s o f t h e sp e c im e n a c c o r d in g t o t h e a t t a c h e d s p e c l f l c a t i o t
C y lin d ric a l T h r e a d e d Dob B o n e I e n s i le S p ec im en
iDHC-gQ0 3 / 2 6 / 0 2A p p ro v e d FPr. Roy
Figure 2.1 Schematic View of Smooth Cylindrical Tensile Specimen
N D H O L E10
S E C T I O N A - A
S C A L E 1 . 0 0
- 0 . 375± O , O O 5
S C A L E A . 00
OIHCNSIONS AKE IN IIKNES UNLESS OTHEIWISE SPECIFIED
SURFACE R0U6NNE3S g T
DO NOT SCALE DRAtING
U N V E R S T Y O F N E V A D A . L A S V E G A S D E P A R T M E N T O F M E C H A N I C A L E N G M E E R N G
E L E C F R O C H E M I C A L P O L A R I Z A T I O N S P E C I M E N
DRAIING BT: MARTIN LEVIS è t f 1 I o n 1 REVA 1 1 O O O l l o i
EFFECTIVE DATE 08/08/01 | S C « 4: 1 & NOTlD I SHEET 1 OF 1
T
Figure 2.2 Polarization Specimen
11
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2.3 Test Environments
Molten LBE is surrounded by target structural material such as Alloy HT-9. This
target structural material can undergo corrosion in molten LBE environment. Due to lack
of facilities to accommodate testing in the molten LBE environment at the University of
Nevada Las Vegas (UNLV), the corrosion experiments in the presence of molten LBE
were performed at the Los Alamos National Laboratory (LANL). Corrosion testing at
UNLV has been performed in neutral and acidic solutions to evaluate the susceptibility of
Alloy HT-9 to SCC, and localized corrosion such as pitting and crevice. Corrosion
studies have been performed at ambient temperature, 60 and 90°C. These tests are aimed
at generating a corrosion database in aqueous environments for comparison purposes.
The chemical compositions of two aqueous environments used in corrosion testing are
given in Table 2.3.
The tensile testing using smooth cylindrical specimens was performed at ambient and
elevated temperatures in the presence of nitrogen to avoid oxidation.
Table 2.3 Chemical Composition of Test Environments (gram/liter)
Environment(pH)
CaClz K2SO4 MgSOj NaCl NaNOj Na2S04 HCl
Neutral (6-6.5) 2.769 7.577 4.951 39.973
31.529 56.742
Acidic (2-2.2) 2.769 7.577 4.951 39.973
31.529 56.742 Added to attain the desired
pH
12
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CHAPTER 3
EXPERIMENTAL PROCEDURES
The high temperature tensile properties of Alloy HT-9 were evaluated by using an
axial/torsional material testing system (MTS). The susceptibility to SCC in neutral and
acidic aqueous environments was evaluated by using slow-strain-rate (SSR) testing
technique at ambient temperature and 90°C. The localized corrosion behavior was
evaluated by using the electrochemical cyclic potentiodynamic polarization (CPP)
technique using a potentiostat manufactured by the Gamry Instruments. Finally,
fractographic and metallographic evaluations were performed by SEM and optical
microscopy, respectively. The detailed experimental techniques are discussed next in the
following subsections.
3.1. Tensile Testing
The tensile properties including the ultimate tensile strength (UTS), yield strength
(YS) and ductility parameters such as percentage elongation (%E1) and percentage
reduction in area (%RA) were evaluated at ambient temperature, 100, 300, 400, 500 and
600°C using an MTS unit. The smooth cylindrical specimens were strained in tension at a
strain rate of lO'^/sec according to the ASTM Designation E 8. ^ A minimum of two
specimens were tested under each experimental condition and an average value was
determined. The experimental data such as the load, time, and extensometer reading were
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recorded in the data file at the rate of 100/sec. The engineering stress versus engineering
strain curves were developed using these data. The magnitude of the yield strength (YS)
was determined by the point of intersection of a line drawn parallel to the linear portion
of this curve at a strain offset value of 0.2% of strain. UTS, %E1, %RA and uniform
elongation were determined using this plot and the dimensions of the cylindrical
specimen before and after testing.
The MTS unit (Model 319.25), shown in Figure 3.1, had an axial load transducer of
55 kip (250 kN) and a torsional load transducer of 20,000 Ibf-in (2200 N-m) capacity. It
had a hydraulically-controlled actuator with 5.5” stroke and approximately 55° angular
rotation. It consisted of a large heavy-duty load frame with an adjustable crosshead
attached to the wedge grip at the top, and a movable actuator with another wedge grip at
the bottom to enable loading and unloading of the test specimen. The axial motion can be
controlled by force, displacement, or an external signal from the strain gage. The
torsional motion can be controlled by torque, angular position, or an external signal from
the strain gage. The specimen was mounted between two wedge grips and was pulled by
the movable actuator. The load cell, contained in the crosshead, measured the applied
force on the tensile specimen. The movement of the crosshead relative to the locked
crosshead generates the strain within the specimen and consequently, the corresponding
load.
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tr 4# 11
ifI ( (.T iim ic 1 k 'a im u Laser
Extensometer( T ia m n e r
High Temperature Grip System
/Nitrogen Supply System
ManualControl( P O D )
IComputer That Controls MTS
Figure 3.1 Material Testing System (MTS)
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The MTS machine was equipped with an 8-channel signal-conditioning box for
monitoring the strain gages, extensometers, and temperature sensors. Signals from this
box were processed directly by the MTS control software programs (Test Star 790.00 v
4.0E and Test Ware SX v 4.0D) that automatically controlled all signals during testing. A
laser extensometer having a scan rate of 100 scans/sec was added to this MTS unit to
measure the elongation of the gage section of test specimen during plastic deformation
under tensile loading. The MTS unit was modified to accommodate high-temperature
testing in the presence of nitrogen using a ceramic-lined custom-made chamber. The
testing temperature inside this chamber was monitored by two K-type thermocouples. A
pair of custom-built water-cooled specimen grips made of maraging steel (M250) was
attached to the MTS machine to prevent these grips from being heated during testing at
elevated temperatures. Temperature profiles were developed to determine the times
needed to achieve the desired test temperatures as a part of the furnace calibration
process. The resultant times and the environment-chamber set point temperatures for
different target temperatures in the presence of nitrogen gas at 20 bar on Argon scale are
shown in Table 3.1.
Table 3.1 Minimum Times Needed to Reach the Desired Temperature
Material Target temperatureCO
Environmental chamber set point temperature
CO
Minimum time to reach the target temperature
(minutes)
AlloyHT-9
100 143 60300 363 60400 467 55500 563 50600 658 50
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3.2. Slow-Strain-Rate Testing
Slow-strain-rate (SSR) testing was performed using a specially-designed system
known as a constant-extension-rate-testing (CERT) machine, as shown in Figure 3.2.
This equipment enabled testing to simulate a broad range of load, temperature, strain-rate
and environmental conditions using both mechanical and electrochemical corrosion
testing techniques.^^^ These machines, designed and manufactured by the Cortest Inc,
offered accuracy and flexibility in testing the effect of strain rate, providing up to 7500
lbs of load capacity with linear extension rates ranging from 10' to 10 * in/sec. To ensure
the maximum accuracy in the test results, this apparatus was comprised of a heavy duty
load-frame that minimized the system compliance while maintaining precise axial
alignment of the load train. An all-gear drive system provided consistent extension rate.
Added features included a quick-hand wheel to apply a pre-load prior to the operation.
The SSR test setup used in this investigation consisted of a top-loaded actuator,
testing chamber, linear variable differential transducer (LVDT) and load cell, as shown in
Figure 3.3. The top-loaded actuator was intended to pull the specimen at a specified strain
rate, so that the spilled solution, if any, would not damage the actuator. A heating coil
was connected to the bottom cover of the environmental chamber for elevated-
temperature testing. A thermocouple was coimected through the top cover of this
chamber to monitor the testing temperature. The load cell was intended to measure the
load through an interface with the front panel. The LVDT was used to record the
displacement of the gage section during testing.
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Constant Extension, Rate Testing MacWncs
A -L V D T B - Top Actuator C - Environmental Chamber D " Bottom Actuator
Figure 3.2 CERT Machine for SSR Testing
Load cell
.Thermooupie/ s te p p e r m otor pow er drive
/LVDT0 I / - ' yBeld point
/eating coil
user in te rface
Testing c lia m b e r
Figure 3.3 SSR Test Setup Showing Different Components
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Prior to the performance of SCC testing, the load-frame-compliance factor (LFCF,
the deflection in the frame per unit load) was determined by using ferritic Type 430
stainless steel specimen. The generated LFCF data, shown in the Figure 3.4, were input to
a load frame data acquisition system prior to testing.
Frame Compliance Test
0.70
0.60
Frame -1 (LFCF=4e-l
y = 4E.06x + 06380.50
.5 0.40
Frame-3 (LFCF=5e-6) y = 5E-06x + 0.2309
0.30
0.20
0.10Frame-2 (LFCF=5e-6
y = 5E-06x + 0.12480.00
0 1000 2000 3000 4000 5000 6000 80007000
Load (lb)
Figure 3.4 Load Frame Compliance Test Data
Smooth cylindrical specimens were used to evaluate the SCC susceptibility of Alloy
HT-9. Since the application of a too fast or a too slow strain rate can adversely influence
the role of mechanical and environmental factors in promoting SCC, a strain rate of
3.3x10'^ sec ' was used to optimize the combined effect of the applied load and the
testing environment. Selection of this strain rate was based on prior research performed at
the Lawrence Livermore National Laboratories.^'*'^ During SCC testing by the SSR
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method, the specimen was continuously strained in tension until fracture, in contrast to
more conventional SCC test conducted under a sustained loading condition. The
application of a slow dynamic strain during the SSR testing to the specimen produced
failure that probably might not occur under a constant load or might have taken a
prohibitively longer duration to initiate cracking in the tested specimens.
Load versus displacement, and stress versus strain curves were plotted during these
tests. Dimensions (length and diameter) of the test specimens were measured before and
after testing. The cracking tendency in the SSR tests was characterized by the time-to-
failure (TTF), and the ductility parameters such as the percent elongation (%E1) and the
percent reduction in area (%RA). Further, the maximum stress (Om) and the true failure
stress (Of) obtained from the stress-strain diagram were taken into consideration. %E1,
%RA, Gm and Of were calculated using the following equations:
% El = -^0V y
xlOO
%RA = Xl OO
(Equation 3.1)
(Equation 3.2)
f A ,(Equation 3.3)
crm A
m
(Equation 3.4)
- 7TX £)„(Equation 3.5)
f (Equation 3.6)
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Where,
4 = Initial cross sectional area
= Cross sectional area at the maximum load
Aj- = Cross sectional area at failure
P„ = Ultimate tensile load
P/ = Failure load
= Initial length
L f = Final length
D„ - Initial diameter
D f = Final diameter
3.3. Cyclic Potentiodynamic Polarization Testing
The susceptibility of Alloy FIT-9 to pitting and crevice corrosion was determined by
performing CPP experiments in neutral and acidic aqueous environments using a
GAMRY potentiostat. This type of testing is based on a three-electrode polarization
concept, in which the working electrode (specimen) acted as an anode and two graphite
electrodes (counter electrodes) acted as cathodes, as shown in Figure 3.5.
The reference electrode was made of Ag/AgCl solution contained inside a Luggin
probe having the test solution in it that acted as a salt-bridge. The tip of the Luggin probe
was placed at a distance of 2 to 3 mm from the test specimen, as shown in Figure 3.6. At
the onset, the corrosion or the open circuit potential (Ecorr) of the test specimen was
determined with respect to the Ag/AgCl reference electrode, followed by forward and
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reverse potential scans at the ASTM specifie4’^ rate of 0.17 mV/sec. An initial delay of
50 minutes was given to attain a stable Ecorr value. The magnitudes of the critical pitting
potential (Epit) and protection potential (Eprot), if any, were determined from the CPP
diagram.
Reference Electrode
Graphite Counter Electrodes
orking Electrode (Test Specimen)
Figure 3.5 Electrochemical Testing Setup
Before conducting the CPP test, the potentiostat was calibrated according to the
ASTM Designation G 5. * Calibration of the potentiostat was performed to generate a
characteristic potentiodynamic polarization curve (Figure 3.7) for ferritic Type 430
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stainless steel specimen in IN (1 Normal) H2SO4 solution at 30°C. Small cylindrical test
specimens made of ferritic Type 430 SS were used to generate the calibration curves.
WxyWn*2 -3 mm LuQ9#n C#pW##y
Figure 3.6 Luggin Probe Arrangement
3 ""ÎTT!»,, , ..T g
0.6 v/h
i ta s i l I s 1 1 : « 1 s i n i t l 1 j .L listi:
Figure 3.7 Standard Potentiodynamic Polarization Plot (ASTM G 5)'18)
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3.4. Optical Microscopy
Characterization of metallurgical microstructures of the test specimens before and
after testing by optical microscopy is of paramount importance. The principle of an
optical microscope is based on the impingement of a light source perpendicular to the test
specimen. The light rays pass through the system of condensing lenses and the shutters,
up to the half-penetrating mirror. This brings the light rays through the objective to the
surface of the specimen. Light rays reflected off the surface of the sample then return to
the objective, where they are gathered and focused to form the primary image. This
image is then projected to the magnifying system of the eyepiece. The contrast observed
under the microscope results from either an inherent difference in intensity or wavelength
of the light absorption characteristics of the phases present. It may also be induced by
preferential staining or attack of the surface by etching with a chemical reagent.
The test specimens were sectioned and mounted using the standard metallographic
techniques, followed by polishing and etching to reveal the microstructures including the
grain boundaries. The polished and etched specimens were rinsed in deionized water, and
dried with acetone and alcohol prior to their evaluation by a Leica optical microscope. A
resolution of up to lOOOX can be achieved in this microscope.
3.5. Scanning electron microscopy
In a scanning electron microscope (SEM), electrons from a metal filament are
collected and focused, just like light waves, into a narrow beam. The beam scans across
the subject, synchronized with a spot on a computer screen. Electrons scattered from the
subject are detected and create a current, the strength of which makes the spot on the
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computer brighter or darker. This creates a photograph-like image with an exceptional
depth of field. Magnifications of several thousand times are possible in SEM. Normally,
SEM provides black and white micrographs. A JEOL-5600 scanning electron
microscope, capable of resolution of up to 50 nm at magnifications of up to 100,000
times, was used for fractographic evaluations.
The extent and morphology of failure in the tested specimens were determined by
SEM. Analysis of failure in metals and alloys involves identification of the type of
failure. The test specimens were sectioned into Vi to 3/4 of an inch in length to
accommodate them in the vacuum chamber of the SEM. Usually, failure can occur by
one or more of the several mechanisms, including surface damage, such as corrosion or
wear, elastic or plastic deformation and fracture. Failures can be classified as ductile or
brittle. Dimpled microstructure is a characteristic of ductile failure. Brittle failure can be
of two types, intergranular and transgranular. An intergranular brittle failure is
characterized by crack propagation along the grain boundaries while a transgranular
failure is characterized by crack propagation across the grains.
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CHAPTER 4
RESULTS
4.1 Hardness vs. Tempering Time
The measured hardness values in Rockwell C scale (Rc) resulting from austenitizing
and tempering of Alloy HT-9 for three different time periods are shown in Table 4.1.
This table shows the average hardness values based on three measurements along the
diameter of the round bar specimen. As anticipated, the hardness value was reduced due
to tempering, showing gradual reduction with increasing tempering time.
Table 4.1 Hardness Due to Thermal Treatments
Heat-Treating Conditions Hardness (Rc)
Austenitized at 1850°F/1 hr/Oil-Quenched (OQ) 52
Quenched and Tempered at 1150°F/1.25 hrs/Air Cooled (AC) 31
Quenched and Tempered at 1150°F/1.75 hrs/AC 28
Quenched and Tempered at 1150°F/2.25 hrs/AC 27
4.2 Ambient-Temperature Mechanical Properties
The results of ambient-temperature mechanical properties of Alloy HT-9 using an
MTS machine are given in the Table 4.2. These data indicate that no significant variation
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in UTS, YS, %E1 and %RA was observed due to different tempering times, even though
the hardness value was reduced with longer tempering time, as indicated above.
Table 4.2 Ambient Temperature Tensile Properties of Alloy HT-9
Tensile Tempering RoomProperties Time Temperature
1.25 hr 138.5UTS (ksi) 1.75 hr 137.4
2.25 hr 135.11.25 hr 111.4
YS (ksi) 1.75 hr 111.22.25 hr 110.51.25 hr 21.07
%E1 1.75 hr 19.652.25 hr 20.481.25 hr 58.54
%RA 1.75 hr 58.692.25 hr 58.52
4.3 Elevated Temperature Tensile Testing
Comparative analyses of the stress-strain diagrams for Alloy HT-9 at different
temperatures are shown in Figures 4.1 through 4.3 as a function of different tempering
times.
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UTS Alloy HT-9, Q u en ched /T em pered (Q&T)H eat No: 2049Tem pering Time: 1.25 hours
140YS
120
FS100 500°C
600°CCO
2
0.2 0.25 0 .3 0.35 0.40.05 0.1 0 .150Strain
Figure 4.1 Comparison of Stress-Strain Diagrams at Different Temperatures
RT UTS140 YS
Alloy HT-9, Q&THeat No: 2049T em pering Time: 1.75 hours
100°C
120
FS100
500°C
CO
I I00°C60
40
20
0.2 0.3 0.40.05 0.1 0.15 0.25 0.350
Strain
Figure 4.2 Comparison of Stress-Strain Diagrams at Different temperatures
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140 1Y S Alloy HT-9, Q&T
H eat No: 2049Tem pering Time: 2 .2 5 hours
120 -300°C
100 -
500°C
I iOO°Ca>
20
0 0.1 0.2 0 .25 0.350.05 0 .15 0.3 0 .4 0.45
Strain
Figure 4.3 Comparison of Stress-Strain Diagrams at Different Temperatures
A careful review of these stress-strain diagrams indicate that the YS and UTS were
gradually reduced with increasing temperatures, as expected. However, the extent of this
reduction was more pronounced at temperatures above 400°C. It is interesting to note
that, even though the failure stress was also gradually reduced at higher testing
temperatures, the failure strain in the temperature regime of ambient to 300°C was
gradually reduced. This phenomenon is commonly explained by strain hardening effect in
martensitie stainless steels, especially in this temperature regime. Beyond 300°C, the
strain value was enhanced, showing significantly higher strains at 600°C, irrespective of
the tempering time.
As indicated in the previous section, the ductility in terms of %E1 and %RA was
determined using these stress-strain diagrams, and the initial and final dimensions of the
test specimen. The magnitudes of UTS, YS, %E1 and %RA, determined from these
tensile testing, are shown in Tables 4.3 and 4.4 as a function of the tempering time.
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Table 4.3 UTS and YS of Alloy HT-9 at Different Temperatures
Temperature( ° C )
Ultimate Tensile Strength (ksi)
Yield Strength (ksi)
Tempering Time (hours) Tempering Time (hours)1.25 1.75 2 .2 5 1.25 1.75 2.25
RT 138.5 137.4 135.1 111.4 111.2 110.5100 132.6 127.4 125.5 107.2 101.6 101.5300 119 115.3 114.3 97.9 95.1 94.3400 112 109.8 107.3 91.7 90.4 89.1500 94.8 92.1 91.2 8 7 .2 85.2 84.7600 66.5 64.7 6 3 .8 65 63.2 6 2 .2
Table 4.4 %E1 and %RA of Alloy HT-9 at Different Temperatures
Temperature
C C )
% Elongation % Reduction in AreaTempering Time (hours) Tempering Time (hours)
1.25 1.75 2 .2 5 1.25 1.75 2 .2 5RT 21.07 19.65 20.48 58.54 58.69 5 8 .5 2100 19.33 20.60 19.93 62.16 62.27 6 2 .8 4300 17.36 17.62 17.80 62.48 63.15 62.11400 18.50 18.42 18.07 63.30 64.07 64.35500 26.90 26.45 25.81 77.60 78.41 78.50600 35.80 36.11 37.39 87.50 8 8 .3 9 8 8 .8 5
The room temperature tensile data have also been included in these tables for
comparison purpose. Also, the magnitude of uniform elongation determined from stress-
strain diagrams are shown in Table 4.5 for all testing temperatures at different tempering
times.
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Table 4.5 YS vs. Uniform Elongation at Different Temperatures
Temperaturem
Uniform ElongationTempering Time (hours)
1.25 1.75 2.25RT 0.0681 0.0638 0.0626100 0.0581 0.0616 0.0571300 0.0483 0.0495 0.0483400 0.0487 0.0465 0.0445500 0.0296 0.0273 0.02775600 0.0162 0.0118 0.0128
These data indicate that the uniform strain was gradually reduced with increasing testing
temperature irrespective of the tempering time.
The data shown in Tables 4.3 and 4.4 are reproduced in a graphical format showing
the effect of temperature on the different tensile properties including UTS, YS, %E1 and
%RA. The effects of temperature on UTS and YS are shown in Figures 4.4 and 4.5,
respectively, once again showing a gradual decline in UTS and YS with increasing
temperature due to lower resistance to deformation at elevated temperatures.
160.0Alloy HT-9, Q&T
Heat No: 2049140.0
120.0
100.0Î “ 80.0
60.0Tempering Time
40.0. 1.25 hr• 1.75 hr* 2.25 hr
20.0
0.0500 600 700200 300 4000 100
Temperature(°C)
Figure 4.4 UTS vs. Temperature
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120.0 -
Alloy HT-9, Q&T Heat No; 2049
100.0
80.0
60.0
40.0 Tempering Time
♦ 1.25 hr• 1.75 hr
» 2 .25 hr
20.0
0.0600300 500 7004000 100 200
Temperature(°C)
Figure 4.5 YS vs. Temperature
Simultaneously, the enhanced ductility at elevated temperatures in terms of %E1 and
%RA, shown in Figures 4.6 and 4.7, can be attributed to enhanced plastic flow at these
temperatures.
40 .00 n
Aiioy HT-9, Q&T H eat No: 204935.00
30.00
25.00
^ 20.00 -
15.00Tempering Time
10.00 -
. 1.25 hr
■ 1.75 hr A 2 .25 hr
5 .00 -
0.00600 700300 500200 4000 100
Tem perature(°C )
Figure 4.6 %E1 vs. Temperature
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100.00 1Alloy HT-9, Q&T
H eat No: 204990.00
80.00
70.00 -
60.00
^ 50.00 -
40 .00 -
Tempering Time30.00
20.00 - . 1.25 hr ■ 1.75 hr * 2 .25 hr
10.00
0.00300 500 6000 100 200 400 700
Tem perature(°C )
Figure 4.7 %RA vs. Temperature
It should be noted that the drop in UTS and YS, as well as increase in ductility were more
pronounced at temperatures exceeding 400°C. The variation of uniform elongation with
testing temperature is shown in Figure 4.8 for specimens tempered for three different
times.
0.08 1
0.07Alloy HT-9, Q&T Heat No: 20490.06 -
m 0.05
LO 0.04
>5 0.03Tempering Time
0.02-* -1 .25 hr
1.75 hr -*-2 .25 hr
0.01
500 700200 400 600100 3000
Temperature (°C)
Figure 4.8 Uniform Elongation vs. Temperature
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4.4 Fractographic Evaluations
The SEM micrographs of broken specimens tempered for different time periods and
tested at ambient temperature and 600°C are shown in Figures 4.9 through 4.14. An
examination of these micrographs reveals that at ambient temperature, the primary
fracture face contained a large number of cracks showing very little plastic deformation.
However, the primary fracture surface was characterized by a very large dimpled area
indicating enhanced ductility at 600°C. A similar behavior was observed with specimens
tested at other elevated temperatures. Those micrographs are shown in the appendix
section.
Figure 4.9 SEM Micrograph of Alloy HT-9 at Room Temperature for Specimen Tempered for 1.25 hrs (35X)
Figure 4.10 SEM Micrograph of Alloy HT-9 at 600°C for Specimen Tempered for 1.25 hrs (35X)
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Figure 4.11 SEM Micrograph of Alloy HT-9 at Room Temperature for Specimen Tempered for 1.75 hrs (35X)
Figure 4.12 SEM Micrograph of Alloy HT-9 at 600°C for Specimen Tempered for 1.75 hrs (35X)
Figure 4.13 SEM Micrograph of Alloy HT-9 at Room Temperature for Specimen Tempered for 2.25 hrs (35X)
Figure 4.14 SEM Micrograph of Alloy HT-9 at 600°C for Specimen Tempered for 2.25 hrs (35X)
35
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4.5 Slow Strain Rate (SSR) Testing
Stress-strain diagrams for Alloy HT-9 tested in the 90°C acidic solution using the
SSR technique are shown in Figure 4.15. These tests were performed using smooth
cylindrical specimens tempered for 1.25 and 2.25 hours, respectively. The magnitudes of
different tensile parameters were derived from these stress-strain diagrams, which are
shown in Table 4.6. These data indicate that the failure stress (of) was increased, but the
ductility parameters were reduced with specimens tempered for longer time. The effects
of tempering time on Of, TTF, % El and % RA are graphically shown in Figures 4.16
through 4.19, respectively.
120
2.25 hr100 -
80
Alloy HT-9, Q&T H eat No: 204960
I40 - Tem pering Time
1.25 hr2 .25 hr
20 -
0.1 0.120.06 0.080 0.02 0.04Strain
Figure 4.15 Comparison of Stress-Strain Diagrams in SSR Testing
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Table 4.6 Results of SSR Testing
Environment/Temperature
Tempering Time (hrs)
%E1 %RA Pf(lbs)
Om(ksi)
Of
(ksi)TTF(hrs)
Acidic Solution (pH-
2.21)/90°C
1.25 10.68 9.86 3870.97 108 96.97 12.10
2.25 10.19 7.88 4313.56 108.18 102.83 11.47
Where,
%E1
%RA
Pf
Om
O f
TTF
Percentage Elongation
Percentage Reduction in Area
: Failure Load
Maximum Tensile Stress
: Failure Stress
: Time-to-Failure
120
100
80 -
60
40
20
0
Alloy HT-9, Q&T Heat No: 2049
0.5 1 1.5Tempering Time (Hrs)
2.5
Figure
4.16 Failure Stress vs. Tempering Time
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14 1
12 -
10 -
o 6
Ei- 4 4
Alloy HT-9, Q&T Heat No: 2049
0.5 1 1.5
Tempering Time (Hrs)
2.5
Figure
4.17 Time to Failure vs. Tempering Time
12 1
10
2 -
Alloy HT-9, Q&T H eat No: 2049
0.5 1 1.5
Tem pering Time (Hrs)
2 .5
Figure 4.18 %E1 vs. Tempering Time
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12
10
2 -
Alloy HT-9, Q&T Heat No; 2049
0.5 1 1.5
Tempering Time (Hrs)
2.5
Figure 4.19 %RA vs. Tempering Time
4.6 Localized Corrosion Study
The calibration curve for the Gamry potentiostat, used in localized corrosion study
according to the ASTM Designation G 5 ^ is shown in Figure 4.20. This curve closely
matches the standard potentiodynamic polarization curve shown in the ASTM
Designation G indicating the accuracy of the potentiostat in evaluating the localized
corrosion behavior of Alloy FIT-9. The cyclic potentiodynamic polarization (CPP)
diagrams for this alloy generated in neutral and acidic solutions at 30 and 90°C are shown
in Figures 4.21 through 4.24. The magnitude of the corrosion potential (Ecorr) and the
critical pitting potential (Epit), determined from these cyclic polarization diagrams, are
shown in Table 4.7. The effect of temperature on Epufor Alloy HT-9 in neutral and acidic
environments is shown in Figure 4.25. An examination of these data indieates that the Epu
value became more active (negative) in the acidic solution, compared to that in the
neutral solution, as expected. This phenomenon may be attributed to a synergistic effect
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of pH and temperature on the localized corrosion susceptibility of this martensitie
stainless steel. No protection potential (Eprot) was observed in these tests.
1000
8 0 0
4 0 0
200
-200
-e o o
-1000
-12000-2 13-5 - 4
Kliigraji riT'2)j
Figure 4.20 Calibration Curve using GAMRY Potentiostat
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CycNc Waozatioci Scan
Ëpit
IEcorr
iœ .O p I ÛQOfi ie.00n 100.0n 1.£B0p 10.00p IDÜ.Op 1.000 m 10.00m 100.0m 1.000
j(Afcfn*3
Figure 4.21 CPP Diagram in 30“C Neutral Solution
Gyde Pofafàaiiop Semi
Epit
#V '
t :
I Ecorr
lOjIOp WOJOp I j W n 1ÔÀ)n lOOjOn, I.OOOp lOJQOp lOOuOp iOOOm lOnOm 1000m IJÎOO
Figure 4.22 CPP Diagram in 90°C Neutral Solution
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Çy<*c Scars
DOOOV
Ecorr
100 .0)1
Figure 4.23 CPP Diagram in 30°C Acidic Solution
Cÿcfic Pofaswrfran Sear
Epit
Ecorr
I
100.0 m
f (Aknf)
Figure 4.24 CPP Diagram in 90°C Acidic Solution
42
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Table 4.7 CPP Test Results
Material/ Heat No Environment Temperature (°C)
Scan Rate (mV/sec)
Ecorr 5 m V(Ag/AgCl)
Epit, mV (Ag/AgCl)
Alloy HT-9/ 2048
NeutralSolution
30 0.166 -570 -890 0.166 -625 -347
AcidicSolution
30 0.166 -495 -12290 0.166 -475 -440
uf
0 -, -50
-100 -
-150
-200
-250
-3 0 0 -
-3 5 0 -
-400
-4 5 0 -
-50020
N eutral Solu tion A cidic Solution
4 0 6 0
T e m p e ra u re (°C)
80 100
Figure 4.25 Epit vs. Temperature
4.7 Metallographic Evaluations
The microstructural evaluation of Alloy HT-9 was performed using optical
microscopy (OM). The optical micrograph of the austenitized and quenched material is
shown in Figure 4.26 (a). The micrographs for Alloy HT-9, quenched and tempered for
three different times of 1.25, 1.75 and 2.25 hours are shown in Figures 4.26 (b), (c) and
(d) respectively. The results of OM on specimens tested at ambient temperature and
43
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600°C are shown in Figure 4.27 (a) and (b), respectively. The examination of all these
micrographs indicates that fine-grained fully-tempered martensitic microstructure was
observed in all cases. The results of OM involving the SSR test specimens revealed
secondary cracks with some branching, as shown in Figures 4.28 (a), and (b).
(a) Austenitized and Quenched (b) 1.25 hours Tempering Time
(c) 1.75 hours Tempering Time (d) 2.25 hours Tempering
Figure 4.26 Optical Micrographs of Alloy HT-9 under Different Heat-Treat Conditions
44
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(a) Tested at Ambient temperature (b) Tested at 600°C
Figure 4.27 Optical Micrographs of Tensile Specimens Tempered for 1.25 hours
(a) 1.25 Hours of Tempering (b) 2.25 Hours of Tempering
Figure 4.28 Optical Micrographs of SSR Test specimens in 90°C Acidic Solution
45
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CHAPTER 5
DISCUSSIONS
Ambient and elevated temperature tensile properties of Alloy HT-9 were determined
to understand the deformation mechanism of this alloy as a function of temperature. The
susceptibility to SCC of this alloy was evaluated in 90°C acidic solution using the SSR
testing technique. Also, the localized corrosion behavior including pitting and crevice
corrosion was determined by electrochemical cyclic potentiodynamic polarization (CPP)
technique.
5.1 Effect of Thermal-Treatment
As anticipated, the hardness of Alloy HT-9 following the austenitizing and quenching
treatment was substantially high due to the formation of hard, but brittle martensite. The
purpose of tempering was to reduce the hardness value so that significant ductility could
be induced in this alloy due to the homogenization of metallurgical microstructure.
Different tempering times were given to the austenitized and quenched material to see if
the tempering time could influence the resultant ductility. As indicated in an earlier
section, the hardness value gradually became reduced with longer tempering time, as
anticipated. However, this reduction in hardness value was not reflected in the tensile
properties of Alloy HT-9 both at the ambient and the elevated temperatures.
46
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Nevertheless, a uniform microstructure consisting of fine-grained and fully tempered
martensite was observed with specimens tempered for three different times.
5.2 Effect of Temperature on Tensile Properties
The results of tensile testing, presented in the previous section, clearly indicate that
the magnitudes of UTS, YS, %E1 and %RA were significantly influenced by the variation
in temperature during tensile testing. The reduced UTS and YS values with increasing
temperature could be attributed to enhanced movement of lattice imperfections such as
dislocations through the grain boundaries to the neighboring grains of this alloy due to
increased plastic flow with increasing temperature. At elevated temperatures, this alloy
was able to undergo plastic deformation more readily due to the enhanced plastic flow.
This reduction in strength at elevated temperatures was usually associated with increased
ductility in terms of %E1 and %RA, as observed by other investigators.^’ ’
In the temperature regime of ambient to 300°C, the ductility of this material was
reduced to some extent. This was characterized by reduced strain in the stress-strain
diagrams for this alloy, shown in the previous section. This behavior can be attributed to
the strain hardening p h e n o m e n o n * ^ ' t h a t can produce large number of defects
such as dislocations and voids, thus, increasing the resistance of this material to plastic
deformation and reducing the extent of ductility. However, beyond 300°C, the ductility of
this material was gradually increased, showing substantially higher %E1 and %RA values
at 500 and 600°C.
The magnitude of YS and UTS became significantly reduced at temperamres above
400°C, suggesting that a temperature in the vicinity of 400°C may represent the critical
47
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temperature beyond which the strength of Alloy HT-9 may be drastically reduced due to
enhanced plasticity. For the same reason, the ductility parameters were also enhanced at
temperatures beyond 400°C. With respect to the effect of tempering time on the tensile
properties, the magnitude of UTS, YS %E1 and %RA was not at all influenced by the
changes in tempering time irrespective of the testing temperature.
5.3 Slow Strain Rate Testing
The results of SCC testing, conducted in a 90°C acidic solution by using the SSR
technique, showed that the failure stress (of) was increased but the ductility was reduced
as the tempering time was increased from 1.25 to 2.25 hours. It is well known that a
longer tempering time can produce improved ductility due to relaxation of internal
stresses that were generated during the quenching operation. This phenomenon can
possibly explain the cause of higher failure stress (of) with specimens tempered for 2.25
hours. However, some discrepancy was observed with ductility in terms of %E1 and
%RA, in that reduced ductility was observed despite increased Of value. Ideally, these
specimens should have given enhanced ductility values with increased tempering time.
No valid explanation can be provided at this time as to this unusual behavior related to
the ductility parameter. In view of these results, it is suggested that further study be
pursued in future to address this issue.
5.4 Electrochemical Polarization Testing
The results of localized corrosion study using the CPP technique revealed that the
magnitude of the critical pitting potential became more active in the acidic solution at
48
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90°C. The more active potential is usually associated with increased susceptibility to
pitting and crevice corrosion due to the synergistic effect of the elevated temperature and
the acidic pH. The evaluation of the polarized specimens by visual examination showed
that the extent of localized attack was more pronounced in the 90°C acidic solution due to
the increased hydrogen ion (H^) concentration in the acidic solution, compared to that in
the neutral solution.
49
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CHAPTER 6
SUMMARY AND CONCLUSIONS
The effect of tempering time on the tensile properties of quenched and tempered
martensitic Alloy HT-9 has been evaluated at temperatures ranging from ambient to
600°C in the presence of nitrogen. SSR testing has been performed to evaluate the SCC
behavior of this alloy in a 90°C acidic environment. The susceptibility to localized
corrosion including pitting and crevice corrosion has been determined by electrochemical
CPP method. Optical microscopy has been utilized to characterize the secondary cracks
during SCC. Fractographic evaluations of the tensile specimens have been performed by
SEM. The significant conclusions derived from this investigation are given below.
> The longer tempering time resulted in reduced hardness of this alloy due to
relaxation of internal stresses resulting from the quenching operation. However,
the metallurgical microstructure and the tensile properties at different
temperatures were not significantly influenced by the variation in tempering time.
> The tensile strength of Alloy HT-9 in terms of YS, UTS and Of was gradually
reduced with increasing temperature, showing significant reduction at
temperatures above 400°C.
> At temperatures, ranging from ambient to 300°C, the magnitude of failure strain
was reduced to some extent due to the strain hardening effect. However, the
50
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ductility parameters in terms of %E1 and %RA were gradually enhanced at
temperatures above 300°C due to enhanced plastic flow.
> The dimpled area became larger with increasing test temperature indicating
enhanced ductility at elevated temperature.
> The failure stress in the SSR testing was higher for specimens tempered for a
longer time.
> All polarized specimens showed pitting and crevice corrosion, irrespective of the
testing environment. The magnitude of Epit became more active at elevated
temperature in both the test environments.
51
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CHAPTER 7
FUTURE WORK
/ The effect of tempering time on the SCC susceptibility of Alloy HT-9 needs
further studies.
SCC data using aqueous environments should be correlated to those obtained in
the molten LBE environment.
/ Transmission electron microscopy should be used to analyze defects and their
interactions in Alloy HT-9 as a function of the testing temperature.
52
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APPENDIX A: TENSILE DATA USING SPECIMENS TEMPERED FOR 1.25 HOURS
AS A FUNCTION OF TESTING TEMPERATURE
Material : Alloy HT-9 Heat Number : 2049 Austenitized I hr at I850F and OQ Tempered at II50F for I.25hrs and AC Testing Temp: Room TemperatureSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H491_RT#I 3.9998 in 0.2498 in 136.1160 ksi 109.5236 ksi 20.84 % 5&53 94
Alloy HT-9 2049 Stress vs Strain
140 n
120100
20
0.2500.100 0.150 0.2000.000 0.050
S train
Material : Alloy HT-9 Heat Number : 2049 Austenitized I hr at 1850F and OQ Tempered at II50F for 1.25hrs and AC Testing Temp: Room TemperatureSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H49I RT#2 4.0003 in 0.2499 in 137.5 ksi IIO.I ksi 22.13 % 59.68 %
A ky HT-9 2049 Stress vs Strain
140
120100
£CO
0.150 0.200 0.2500.050 0.1000.000
S train
53
R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission.
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 1.25hrs and AC Testing Temp: Room TemperatureSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H491_RT#4 4.0002 in 0.2506 in 142 ksi 114.7 ksi 20.25 % 59.42 %
Alloy HT-9 2049 Stress vs Strain
160 1
140 -
120 100
stn
0,2500.100 0.150 0.2000,000 0.050
S tra in
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 1.25hrs and AC Testing Temperature; 100°CSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H491_100#5 4.0013 in 0.2509 in135.3 ksi111.3 ksi 1R79%6 6154 94
Alloy HT-9 2049 Stress vs Strain
160 -
140 -
120 "5 100 ■
0.200 0.2500.100 0.1500.000 0.050
S train
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 1.25hrs and AC Testing Temperature: 100°CSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H491_100#6 4.0022 in 0.2505 in 131.7334 ksi 105.3942 ksi 1R81%6 61.72%
Altay HT-9 2049 Stress vs Strain
160 1
140 -
120 -
100
60 -
40
2
0.2500.100 0.150 0.2000.000 0.050
S train
54
R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission.
Material ; Alloy HT-9 Heat Number : 2049 Austenitized Ihr at I850F and OQ Tempered at 1150F for 1.25hrs and AC Testing Temperature: 100°CSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H491_100#7 4.0002 in 0.2502 in 130.8 ksi 105.0 ksi 20.40 % 61.21 %
Alloy HT-9 2049 Stress vs Strain
160 -|
140 -
120 ■
100 -
4 0 -
0.2500.000 0.050 0.100 0.150 0.200S train
Material ; Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 1.25hrs and AC Testing Temperature: 300°CSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H491 300#8 4.0010 in 0.2507 in118.3 ksi 97.0 ksi17.03 % 6258 94
Alloy HT-9 2049 Stress vs Strain
160 1
140
120 -
100
CO
0.2500.100 0.150 0.2000.000 0.050
S train
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 115GF for 1.25hrs and AC Testing Temperature: 300°CSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H491_300#9 4.0000 in 0.2503 in 119.7 ksi 98.8 ksi 17.69 % 6238 94
A ky HT-9 2049 Stress vs Strain
160 1 140 120- 100
0.2500.000 0.100 0.150 0.2000.050
Strain
55
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Material : Alloy HT-9 Heat Number ; 2049 Austenitized Ihr at 1850F and OQ Tempered at 115OF for 1.25hrs and AC Testing Temperature: 400°CSpeeimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H491_400#10 3.9972 in 0.2500 in 111.7 ksi 91.9 ksi 18.57% 62.94 %
Alloy Hr-9 2049 Stress vs Strain
160 n140 -
_120- « 100
0.100 0.200 0.2500.050 0.1500.000S train
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 1.25hrs and AC Testing Temperature: 400°CSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H491_400#13 4.0022 in 0.2508 in 112.1958 ksi 91.4095 ksi 18.44% 63.67 %
Alloy HT-9 2049 Stress vs Strain
160-,
140
120 -100
%S
CO
0.2500.100 0.150 0.2000.0500.000Strain
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 1.25hrs and AC Testing Temperature: 500°CSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H491_500#ll 4.0000 in 0.2506 in 94.6 ksi 88.2 ksi 25.96 % 76.37 %
Alloy HT-9 2049 Stress vs Strain
160 n
140
120100
S 60-
" 40
0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350 0.400
S train
56
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Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 115OF for 1.25hrs and AC Testing Temperature; 500°CSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H491 500#14 3.9955 in 0.2512 in 94.9 ksi 86.2 ksi 2%89%6 7&86 94
Alloy HT-9 2049 Stress vs Strain
160
140120100
0.000 0,050 0.100 0.150 0.200 0.250 0.300 0.350 0.400
Strain
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 1.25hrs and AC Testing Temperature: 600°CSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H491_600#13 3.9972 in 0.2497 in 66.9 ksi 65.2 ksi 3548%6 8 7 .8 6 %
Alloy HT-9 2049 Stress vs Strain
160140
_ 120
« 100
£
0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350 0.400
Strain
57
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APPENDIX B: TENSILE DATA USING SPECIMENS TEMPERED FOR 1.75 HOURS
AS A FUNCTION OF TESTING TEMPERATURE
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at I I 5OF for 1.75hrs and AC Testing Temp: Room TemperatureSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H492_RT#I 4.0002 in 0.2511 in 140.1 ksi 115.0 ksi 21.14% 59.05 %
Alloy HT-9 2049 Stress vs Strain
160 n
140
120 -
100
Γ 40 -
0.100 0.150 0.200 0.2500.000 0.050
Strain
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 1.75hrs and AC Testing Temp: Room TemperatureSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H492_RT#2 4.0005 in 0.2510 in 134.7 ksi 110.1 ksi 18.15% 5833 94
Alloy HT-9 2049 Stress vs Strain
160 1
140
1 2 0 -
100
m
0.150 0.200 0.2500.000 0.050 0.100Strain
58
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Material : Alloy HT-9 Heat Number ; 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 1.75hrs and AC Testing Temperature: 100°C Specimen ID : H492_100#3Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
3.9965 in 0.2511 in 128.8 ksi 97.3 ksi 2L37 94 62.21 %
Alloy HT-9 2049 Stress vs Strain
160
140
12010080
60
40
200 f— 0.000 0,050 0.100 0.200 0.2500.150
Strain
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 1.75hrs and AC Testing Temperature: 100°C Specimen ID : H492 100#9Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
4.0017 in 0.2517 in 127.2 ksi 103.1ksi 20.27 % 62.48 %
Alloy HT-9 2049 Stress vs Strain
160
140
120100
40
0.2500.000 0.050 0.100 0.150 0.200Strain
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 1.75hrs and AC Testing Temperature: 100°C Specimen ID : H492_100#10Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
4.0140 in 0.2513 in126.3 ksi104.3 ksi 20.15% 62T2 94
Alloy HT-9 2049 Stress vs Strain
160 1
140
120 -100-
I 40 -
0.2500.000 0.050 0.100 0.150 0.200S train
59
R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission.
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 1.75hrs and AC Testing Temperature: 300°C Specimen ID : H492 100#4Length : 3.9967 inDiameter : 0.2496 inUltimate Tensile Strength Yield Strength %Elongation % Reduction in Area
116.2 ksi 96.0ksi17.78 %63.79 %
Alloy HT-9 2049 Stress vs Strain
160
140
12010080
60
40
200 4— 0.000 0.200 0.2500.1500.050 0.100
Strain
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 1.75hrs and AC Testing Temperature; 300°C Specimen ID : H492 400# 11Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
4.0103 in 0.2512 in 114.3 ksi 94.1 ksi 17.45 % 62.50 %
Alloy HT-9 2049 Stress vs Strain
160
140 - 120 100 80 -
0.2500.2000.050 0.100 0.1500.000Strain
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 1.75hrs and AC Testing Temperature: 400°C Specimen ID : H492_400#5Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
4.0000 in 0.2521 in 108.5 ksi 91.1 ksi 1&63Ï6 63.49 %
Alloy HT-9 2049 Stress vs Strain
160 1
140 -
120
100
£ 60CO
0.200 0.2500.100 0.1500.000 0.050
Strain
60
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Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 1.75hrs and AC Testing Temperature; 400°C Specimen ID : H492 5GO# 12Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
4.0093 in 0.2512 in 111.1 ksi 89.7 ksi 18.19 % 64.65 %
Alloy HT-9 2049 Stress vs Strain
160 1
140
120 -
100 -£S.</)
0.150 0.200 0.2500.000 0.050 0.100
Strain
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 1.75hrs and AC Testing Temperature: 500°C Speeimen ID : H492_500#13Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
3.9980 in 0.2522 in92.5 ksi85.6 ksi 26H8 94 78.11 %
Alloy HT-9 2049 Stress vs Strain
180
140
120
to
0.000 0.050 0.100 0.150 0.200 0.250 0.300
Strain
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 1.75hrs and AC Testing Temperature: 500°C Specimen ID : H492 500#14Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
4.0005 in 0.2510 in91.7 ksi84.7 ksi 26.71% 78.71 %
Alloy HT-9 2049 Stress vs Strain
160
140
120~ 100
20
0.000 0.050 0.100 0.150 0.200 0.250 0.300
S train
61
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Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 1.75hrs and AC Testing Temperature: 600°C Specimen ID : H492_600#7Length : 3.9977 inDiameter : 0.2504 inUltimate Tensile Strength Yield Strength %Elongation % Reduction in Area
66.1 ksi64.1 ksi 35H8 94 87.93 %
Alloy HT-9 2049 Stress vs Strain
160
140
120100
(O
0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350 0.400
Strain
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 1.75hrs and AC Testing Temperature: 600°C Specimen ID : H492 600#15Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
4.0025 in 0.2515 in63.2 ksi62.3 ksi37.04 % 88.85 %
Alloy HT-9 2049 Stress vs Strain
160
140
120 ~ 100
0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350 0.400
Strain
62
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APPENDIX C: TENSILE DATA USING SPECIMENS TEMPERED FOR 2.25 HOURS
AS A FUNCTION OF TESTING TEMPERATURE
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 2.25hrs and AC Testing Temperature: Room TemperatureSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H493_RT#1 3.9965 in 0.2513 in 132.8557 ksi 105.5616 ksi 20.40 % 57.66 %
Alloy HT-9 2049 Stress vs Strain
160-,
140
120
100
OT
0.050 0.200 0.2500.000 0.100 0.150
Strain
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 2.25hrs and AC Testing Temp: Room TemperatureSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H493_RT#2 3.9937 in 0.2510 in 139.0038 ksi 110.4325 ksi 20.29 % 58J6 94
Aiioy HT-9 2049 Stress vs Strain
160
140
120100JS
sCO
0.050 0.200 0.2500.000 0.100 0.150
Strain
63
R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission.
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 2.25hrs and AC Testing Temp: Room TemperatureSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H493_RT#3 3.9958 in 0.2509 in 133.461 ksi 115.444 ksi 20.75 % 59.15 %
Alloy HT-9 2049 Stress vs Strain
140 -
120
f 100
0.2000.150 0.2500.000 0.050 0.100
Strain
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 2.25hrs and AC Testing Temperature: 100°CSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H493 100#4 4.0080 in 0.2510 in 125.4905 ksi 101.1477 ksi
6L3694
Alloy HT-9 2049 Stress vs Strain
160-,
140
120
100
%
0.150 0.200 0.2500.050 0.1000.000
S train
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 2.25hrs and AC Testing Temperature: 100°CSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H493_100#5 3.9977 in 0.2522 in 125.4883 ksi 101.9283 ksi 18.99% 64.32%
Alloy HT-9 2049 Stress vs Strain
160-,
140 -
120
100 -,
« ®o- 60
40
stn
0.150 0.200 0.2500.050 0.1000.000
Strain
64
R eproduced with perm ission o f the copyright owner. Further reproduction prohibited without perm ission.
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 2.25hrs and AC Testing Temperature: 300°CSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H493_300#6 4.0090 in 0.2515 in 114.3509 ksi 93.8788 ksi 183494 6Z5194
Alloy HT-9 2049 Stress vs Strain
160 1
140 120 -
100 -
0.050 0.150 0.200 0.2500.000 0.100
Strain
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 2.25hrs and AC Testing Temperature: 300°CSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H493_300#7 4.0022 in 0.2513 in 114.2185 ksi 94.5891 ksi 17.25 % 61.70%
Aloy HT-9 2049 Stress vs Strain
160 -,
140
120
100 ■
£OT
0.150 0.200 0.2500.000 0.050 0.100
Strain
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at I850F and OQ Tempered at 1150F for 2.25hrs and AC Testing Temperature: 400°CSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H493_400#8 4.0128 in 0.2510 in 106.5091 ksi 87.4098 ksi 18.17% 65.22 %
Alloy HT-9 2049 Stress vs Strain
160-,
140-
120
=5 100
40
0.2500.150 0.2000.000 0.050 0.100
Strain
65
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Material ; Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 115OF for 2.25hrs and AC Testing Temperature: 400°CSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H493_400#9 4.0105 in 0.2509 in 108.1399 ksi 90.7809 ksi 17.96 % 63.47 %
Alloy HT-9 2049 Stress vs Strain
160
140
120
100£
m
0.100 0.2500.000 0.050 0.150 0.200
S train
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 2.25hrs and AC Testing Temperature: 500°CSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H493_500#10 4.0160 in 0.2510 in 91.3207 ksi 84.4779 ksi 25.28 % 7&39T4
160
140
120
=5 100
% 80 £ 60
40
20
<o
00.000
Alloy HT-9 2049 Stress vs Strain
0.050 0,100 0.150
Strain
0.200 0.250 0.300
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 2.25hrs and AC Testing Temperature: 500°CSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H493_500#ll 4.0017 in 0.2507 in 91.0894 ksi 84.9419 ksi 25.54 % 7&59 94
Alloy HT-9 2049 Stress vs Strain
160
140
120 M 100
80
60
40
20
Strain
0.250 0.300
66
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Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 2.25hrs and AC Testing Temperature: 600°CSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H493_600#12 4.0083 in 0.2508 in 63.1944 ksi 61.3020 ksi 3735 89H4 94
Alloy HT-9 2049 Stress vs Strain
160 -
140
120 -
^ 100
0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350 0.400
Strain
Material : Alloy HT-9 Heat Number : 2049 Austenitized Ihr at 1850F and OQ Tempered at 1150F for 2.25hrs and AC Testing Temperature: 600°CSpecimen ID Length Diameter Ultimate Tensile Strength Yield Strength %Elongation % Reduction in Area
H493_600#13 4.0075 in 0.2513 in 64.4086 ksi 63.1046 ksi 37.42 % 8R5694
Alloy HT-9 2049 Stress vs Strain
160 -j
140
120
“ 100
£ 60
" 40
0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350 0.400
Strain
67
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APPENDIX D: SEM MICROGAPHS FOR SPECIMENS TEMPERED FOR 1.25
HOURS AS A FUNCTION OF TESTING TEMPERATURE
(a) Tested at IOO°C (b) Tested at 300°C
m a m
(c) Tested at 400°C (d) Tested at 500°C
SEM Micrographs of Alloy HT-9 Tempered for 1.25 hours
68
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APPENDIX E: SEM MICROGAPHS FOR SPECIMENS TEMPERED FOR 1.75
HOURS AS A FUNCTION OF TESTING TEMPERATURE
&(a) Tested at IOO°C (b) Tested at 300°C
(c) Tested at 400°C (d) Tested at 500°C
SEM Micrographs of Alloy HT-9 Tempered for 1.75 hours
69
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APPENDIX F: SEM MICROGAPHS FOR SPECIMENS TEMPERED FOR 2.25
HOURS AS A FUNCTION OF TESTING TEMPERATURE
m - Æ -
m
(a) Tested at IOO°C (b) Tested at 300°C
(c) Tested at 400°C (d) Tested at 500°C
SEM Micrographs of Alloy HT-9 Tempered for 2.25 hours
70
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BIBLIOGRAPHY
1) Transmutation Tour, Advanced Fuel Cycle Initiative (http://apt.lanl.gov/atw/)
2) Hisham Zeriffi, Annie Makhijani, “Nuclear Alchemy Gamble: An Assessment of Transmutation as Nuclear Waste Management Strategy”, Institute of Energy and Environmental Research, May 2000.
3) “Processing of Nuclear Wastes”, UIC Nuclear Issues Briefing Paper# 72, December 2001.
4) M.Victoria, D.Gavillet, P.Spatig, F.Rezai-Aria, S.Rossman, “Microstructure and Mechanical Properties of Newly Developed Low Activation Martensitic Steels”, Journal of Nuclear Materials, Vol.233-237, p 326-330, 1996.
5) “Choice of First Wall Material Physical Mechanical Thermal Chemical Neutronic Radiation Damage Cost Availability”, Lecture42, University of Wisconsin (fti.neep.wisc.edu/neep423/FALL98/Lecture42.pdf).
6) R.J.DiMelfi, E.E.Gruber, J.M.Kramer, “Microstructural Evaluation in a Ferritic- Martensitic Stainless Steel and its Relation to High-Temperature Deformation and Rupture Model”, RE-207, Argonne National Laboratory, Argonne, IL.
7) ASTM Designation E 8, “Standard Test Methods for Tensile Testing of Metallic Materials”.
8) ASTM Designation G 5, “Standard Test Methods for Tensile Testing of Metallic Materials”.
9) Corrosion Testing Equipment, Cortest, Incorporated (www.cortest.com)
10) A. K. Roy et., al. Cracking of Titanium Alloys under Cathodic Applied Potential , Framatome Cogema Fuels, September 1999.
11) ASTM Designation: G61-78, Standard Practice for Conducting CyclicPotentiodynamic Polarization Measurements for Localized Corrosion.
12) J.L. Martin and M. Victoria, ‘Deformation Mechanisms of Ferritic - Martensitic Steel between 290 and 870K’, Material Science & Engineering. A. structural materials; properties, microstructure and processing, p 159 - 163, May 30, 1993.
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13)M. Victoria, D. Gavillet, P. Spating, F. Rezai-Aria, S. Rossmann, “Microstructure and Mechanical Properties of Newly Developed Low Activation Martensitic Steels”, Journal of nuclear materials, Vol.233-237, p 326-330, 1996.
14) Yu. Lakhtin, “Engineering Physical Metallurgy and Heat-Treatment”, MIR Publishers, Moscow.
15)R. Dutton and M. P. Puls, in A. W. Thompson and I. M. Bernstein (eds.). Effect of Hydrogen on Behavior of Materials, TMS-AIME, 1976, p. 516.
16) A. K. Roy, et. al., "Electromechanical Corrosion Studies of Container Materials in Repository-Relevant Environments," LLNL Report UCRL-ID-122860, December 1995.
17) Ajit K. Roy, Srinivas R. Kukatla, Bhagath Yarlagadda, “High Temperature Deformation Characteristics of Martensitic Stainless Steels,” SAMPE 2004, Long Beach, CA, USA
72
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VITA
Graduate College University of Nevada, Las Vegas
Bhagath Yarlagadda
Local Address:4214 Grove Circle Apt # 3 Las Vegas, Nevada 89119
Degrees:Bachelor of Technology, Mechanical Engineering, 2002 Jawaharlal Nehru Technological University, Hyderabad, India
Master of Science, Engineering, 2004 University of Nevada, Las Vegas
Publications:Ajit. K. Roy, Srinivas R. Kukatla, Bhagath Yarlagadda, “High Temperature Deformation Characteristics of Martensitic Stainless Steels,” SAMPE 2004, Long Beach, CA, USA
S. R. Kukatla, B. Yarlagadda, V. N. Potluri, “Temperature Effect on Mechanical Properties of Target Structural Materials,” ANS Student Conference 2004, UW, Madison, WI, USA
Thesis Title: Elevated Temperature Mechanical Properties and Corrosion Characteristics of Alloy HT-9
Thesis Examination Committee:Chair Person, Dr. Ajit K.Roy, Ph. D.Committee Member, Dr. Anthony Hechanova, Ph. D.Committee Member, Dr. Brendan J.O’Toole, Ph. D.Graduate Faculty Representative, Dr. Venkatesan Muthukumar, Ph. D.
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